1. Field of the Invention
The invention concerns cosmetic sunscreen compositions delivering UV protection and also soft focus properties.
2. The Related Art
Ultraviolet radiation can be damaging to skin. Immediate damage may be in the form of erythema. More long term is the concern of initiating cancerous growth. For these reasons, photoprotective agents known as sunscreens have been incorporated into cosmetic products.
Facial cosmetics desirably deliver not only photoprotection but also function to enhance overall skin appearance. Most persons have facial imperfections. These may include uneven tone, enlarged pores, fine lines and wrinkles.
Soft focus is a technique which can hide imperfect skin. Incoming light is distorted by scattering (lensing). Particulate components of the cosmetic operate as lenses to bend and twist light into a variety of directions.
U.S. Pat. No. 5,997,890 (Sine et al.), U.S. Pat. No. 5,972,359 (Sine et al.), and U.S. Pat. No. 6,174,533 B1 (SaNogueira, Jr.) are all directed to topical compositions to provide good coverage of skin imperfections. The solution proposed by these documents is the use of a metal oxide with a refractive index of at least about 2 and a neat primary particle size of from about 100 to about 300 nm. Preferred particulates are titanium dioxide, zirconium oxide and zinc oxide.
U.S. Patent Application 2005/0163813 A1 (Kosbach et al.) reports use of fumed alumina particles for enhancing the soft-focus effect of certain cosmetic compositions.
Crosslinked silicone elastomers also have been identified as aids in achieving soft focus. U.S. Patent Application 2005/0163730 A1 (Rosevear et al.) discloses a synergistic interaction between crosslinked silicone elastomer and zinc oxide having average particle size less than 300 nm. A related disclosure is found in U.S. Patent Application 2005/0249684 A1 (Dobkowski et al.) wherein a taurate polymer enhances optical effects in combination with a silicone elastomer and zinc oxide.
A disadvantage of silicone elastomers is their interaction with organic sunscreens. Generally the silicone elastomers are suspended/dissolved in a silicone fluid carrier. These silicone fluid carriers are extractable into the organic sunscreens thereby shriveling the elastomer particles adversely affecting soft focus properties. Consequently, there is a challenge to provide a soft focus effect while maintaining a relatively high degree of photo protective properties in a cosmetic composition.